Wipe on color proofing process and product

ABSTRACT

A process of color proofing by a wipe on method and color proof product produced thereby wherein the color proof process comprises coating at least one side of a paper with a bichromate gelatin emulsion and thereafter drying the same; exposing the emulsion through a color separation negative so as to expose a portion of the gelatin and effect hardening of the exposed gelatin; applying a first desired color, i.e., pigment formulation, to the gelatin emulsion; washing the coated paper to remove the unhardened gelatin and thereafter drying the same; coating the paper again with the bichromate gelatin emulsion, drying the same and exposing this further emulsion through a second color separation negative so as to again cause the exposed gelatin to harden; applying a second desired color to the gelatin and drying the coated paper and finally washing the coated paper to remove the unhardened gelatin with subsequent drying. The steps of applying the bichromate gelatin emulsion, exposing the emulsion through a color separation negative, applying a desired color and washing the paper to remove unhardened gelatin can be repeated for as many colors as desired. One or both sides of the paper can be advantageously processed in the above manner to provide a color proof substantially indistinguishable from the actual copies made with subsequently produced printing plates. Additional variations of the above process are applicable including exposing the emulsion through more than one separation negative at a time with overprinting if desired.

United States Patent [191 Henry WIPE ON COLOR PROOFING PROCESS AND PRODUCT [75] Inventor: Vincent Henry, New York, NY. [73 Assignee: VJG, Inc., New York, NY.

[22] Filed: May 25, 1972 21 Appl. No.: 256,846

5/1959 Tupis 96/35 Primary Examiner-Ronald H. Smith Assistant Examiner-Alfonso T, Suro Pico Attorney, Agent, or Fir m-Sherman & Shalloway [57] ABSTRACT A process of color proofing by awipe on method and color proof product produced thereby wherein the color proof process comprises coating atleast one side May 21, 1974 of a paper with a bichromate gelatin emulsion and thereafter drying the same; exposing the emulsion through a color separation negative 50 as to expose a portion of the gelatin and effect hardening of the exposed gelatin; applying a first desired color, i.e., pigment formulation, to the gelatin emulsion; washing the coated paper to remove the unhardened gelatin and thereafter drying the same; coating the paper again with the bichromate gelatin emulsion, drying the same andexposing this further emulsion through a second color separation negative so as to again cause the exposed gelatin to harden; applying a second desired color to the gelatin and drying the coated'paper and finally washing the coated paper to remove the unhardened gelatin with subsequent drying. The steps of applying the bichromate gelatin emulsion, exposing the emulsion through a color separation negative,'applying a desired color and washing the paper to remove unhardened gelatin can be repeated for as many colors as desired. One or both sides of the paper can be advantageously processed in the above manner to provide a color proof substantially indistinguishable from the actual copies made with subsequently produced printing plates. Additional variations of the above process are applicable including exposing the emulsion through more than one separation negative at a time with overprinting if desired.

21 Claims, No Drawings WIPE ON COLOR PROOFING PROCESS'AND PRODUCT The present invention relates to a wipe on color proofing process and product produced thereby, such process allowing the user to put one or more colors in register and overprint on one or both sides of ordinary printing papers without the use of a whirler, without the need to make plates or engravings and without the use of a printing press.-

The production of color proofs is widely used in the advertising field and in the creative design arts as a preliminary in the preparation of a final color image print.

' It is a general practice in the color image printing art to provide one or several samples or test prints before deciding on the final design or format to be printed. Accordingly, the process of creating numerous designs and utilizing many different color combinations can prove to be verytime consuming and expensive. As a practical matter, it is common to limit the sample prints to one, two or three different specimens. Therefore, the nature of this method dictates that specimens must be precisely accurate and correlate to the final printed materials as closely as possible.

Several methods of producing these color image prints or proofs are known in the art. One widely used process comprises the printing of a prooffrom actual printing plates which are made from a separation negative for each of four separate colors. This process, however, consumes great amounts of time and money as it requires a trial and error method of remaking printing plates for each adjustment of hue, shadowing and colon Another such color proofing method employs the use of photo-sensitive materials containing photorsensitive dyes on transparent supporting members. After various sensitization and washing processes, the eyed image containing transparencies aresuperposed in register to produce color proofing foils. These foils, although produced considerably faster than the printed proofs previously mentioned, are limited in their color reproduceability by the availability of photo-sensitive dyes which are very difficult to match to the various printing inks. A similarly undesirable property of the foils is that internal reflections are often caused by the superposed 1 transparencies.

A third known process of this type includes the use of the same printing ink in the proofing process as in the printing operation. Such ink is applied to a coated transparent support wherein the coating hasbeen presensitized through a color separation negative with subsequent removalof the unexposed coating. However,

one such coated transparent support for each color,

separation negative is required in this process, therefore necessitating that the supports be superposed in v fast, accurate and especially versatile color proofing system.

The versatility of this system may be more specifically attributed tothe ability to use any grade of white or colored offset or letter press paper or bleached and and letter press ink formula. Since the proofing colors and the printing inks are manufactured with the same monotone pigments and the paper used in proofing can be the same paper used in the actual printing, the user is guaranteed a final result where the proofed and finished printing are equal, with indiscernible variation, if any. While, as previously mentioned, coated paper is not recommended for the process, a special clear emulsion can be wiped on the finished proof which, after drying, gives a shine to the finish and very closely represents the colors-as they would appear on coated paper.

Such color proofing process in accordance with the present invention comprises coating at least one side of a paper with a bichromate gelatin emulsion and thereafter drying the same; exposing the emulsion through a color separation negative so as to expose a portion of the gelatin and effect hardening of the exposed gelatin; applying afir'st desired color, i.e., pigment formulation, to the gelatin emulsion; washing the coated paper to remove-the unhardened gelatin and thereafter drying the same; coating the paper-again with the bichromate gelatin emulsion, drying the same and exposing this further emulsion through a second color separation negative so'as to again cause the exposed gelatin to harden; applying a second desired color to the gelatin and drying the coated paper and finally washing the coated paper to remove the unhardened gelatin with subsequent drying. The steps of the bichromate gelatin emulsion, exposing the emulsion through a color separation negative, applying a desired color and washing the paper to remove unhardened gelatin can be repeated for as many colors as desired. One or both sides of the paper can be advantageously processed in the above manner to provide a color proof substantially indistinguishable from the actual copies made with subsequently produced printing plates. Additional variations of the above process are applicable including exposing the emulsion through more than one separation negative at a time with overprinting if desired.

Accordingly, it is an object of this invention to provide a color proofing process which may be used on any grade of paper including letter press paper, ordinary printing paper, craft paper, cardboard and the like.

Further, it is another object of this invention to provide a color proofing system for which any color of printing ink can be easily matched by the color proofing pigment solution.

It is yet another object of this invention to provide a color proofing system inwhich color proofs may be made on both sides of the printingpaper.

It is still further another object of thisinvention to provide an overall color proofing system in which proofs which closely match the final prints can quickly, easily and inexpensively be madebefore making printing plates and without the use of a printing press.

It is still a further object of the present invention to provide a color proofing process which includes the steps of applying a bichromate gelatin emulsion to at least one side of a paper, exposing the emulsion through a color separation negative to effect hardening of the exposed gelatin, applying a first desired color to the gelatin emulsion and washing the coated paper to remove the unhardened gelatin, with repetition of the foregoing steps for each desired color.

These objects and the many advantages may be achieved by a process for color proofing comprising:

a. coating apaper'with a bichromate gelatin emulsion and drying the same;

b. exposing the emulsion to a color separation negative to cause the exposed gelatin to harden;

c. applying a color to the gelatin and drying the coated paper;

d. washing out the coated paper in hot water to remove the unhardened gelatin; and

e. drying the coated paper.

The above cited steps (a), (b) and (c) may be repeated for each additional color desired noting that several variations exist among the color separation negatives and the' colors for wiping on the exposed emulsion. By the appropriate choice of sequence of colors, the method can be simplified in that wherein overprinting colors, such as black, are selected, one wash out step may be eliminated from the process and the first color or colors and the subsequent overprinted color can be washed out at the same time in a single step. Another variation is possible by exposing the emulsion through more than one separation negative at the same time and applying the appropriate colors to the areas which correspond to the colored areas of the color separation negative and subsequently washing out all of the colors from the unexposed portions in single step. It is noted, however, that care must be taken in this procedure to prevent the colors from touching each other unless overprinting of such colors is desired.

One distinct advantage of the present invention is the ability to print on both sides of the paper without increasing the wash out times necessary to the process. This can be accomplished merely by performing the emulsion coating, exposing and color application steps to bothsides of the paper prior to the wash out procedure. Thus, twice as many proofs can be made on the same amount of paper than heretofore possible in one side proofing processes and with a significant savings in time.

To facilitate the handling of the paper during the proofing process, it is desirable to fasten the paper flat to a thin plastic sheet.'The bichromated gelatin emulsion in a water soluble fonn may then be wiped onto the entire surface of the paper and dried by fan, hot air blower or other suitable means. After drying, the emulsion is exposed through the separation negative preferably using the same light source as is used to make a printing plate. Only the clear portions of the negative allow light to pass through thereby hardening the emulsion and rendering it insoluble in water. The parts not effected by light remain soluble in water and thus enable easy removal in the wash out step. In three and four color process printing, the negative mentioned above represents the first color down in the actual printing and is chosen for color by the camerman, artist or color separator. This color is then wiped onto the entire sheet and allowed to dry in the same manner as the bichromated gelatin emulsion. The paper may then be immersed in hot water while still fastened to the plastic sheet and a wash out of the unhardened emulsion takes place. As the unhardened emulsion washes out, so does the color on its surface. Where the emulsion is hardened by light, the color on its surface remains and after drying, presents a proof of the first color. In four color process printing, the remaining three colors are produced in register in the same manner as the first color on the same sheet of paper. If no overprinting as previously discussed is desired in the four color process, it is necessary to put the color capable of overprinting down first. For example, if black, yellow, magenta and cyan are the desired colors, the emulsion must first be exposed through the black color separation negative with the first color down being black. Then, the yellow, magenta and cyan will follow. The order of the three latter colors is not critical, but it is noted that a new emulsion is used for each of the subsequently applied colors following the same exposure, color application and drying sequence as in the black or first down proof. in three color process printing, there is no black separation negative involved. The black areas in the proof and in the printing are the result of the yellow, magenta and cyan printing one over the other. Since most color work today is done on two or four color printing units, three color process printing is seldom, if ever, used. However, proofing for it can be done as mentioned above. i

A particular advantage of this invention is the versatility in the choice of materials to produce the color proofs on. Any offset or letter press sheet, whether white or colored with a basic weight of pounds or over will give best results. This includes bleached or unbleached craft paper for the corrugated or packaging field and box board materials for the packaging field. When preparing a proof on both sides of a paper it is necessary to utilize a paper having a basic weight of at least 100 pounds. Lighter weights can be used where registration and show-through is not critical. Also in lighter weight papers, the water soluble emulsion has a tendency to exaggerate the warping of paper and result in undesirable shrinkage.

This process is suitable on both coated and uncoated paper. While the process will work on coated paper, it is not recommended because the water soluble light sensitive emulsion will not adhere as well on coated paper. In the end result both emulsion and color may washout, even in the hardened areas on the coated paper.

For the purpose of flexability and ease of handling, it is recommended that the size of the paper not exceed 19 inches X 25 inches. However, the process will work on any size paper depending upon the requirement of a specific order, the size of a particular printing shop and the particular capabilities of a printing shop depending on its equipment.

Regarding foil, acetate and plastics and other nonporous materials, if these materials are first treated according to the process described in U.S. Pat. No. 3,560,417, then in the application of the process of the present invention, the water soluble light sensitive emulsion can be used on these items as well.

Another advantageous characteristic of the present invention, i.e., the color versatility, results from the use of a lower alkyl alcohol, water and a dry pigment which are mixed together prior to the application to the emulsion layer. Other filler and masking materials, such as zinc oxide, ferric oxide, calcium oxide and the like, may also be added to the composition. The major component of the pigment composition is the lower alkyl alcohol, such as methyl, ethyl, propyl and isopropyl alcohols. The water portion of the composition must be sufficient to enable the pigment to adhere to the emulsion and to provide a fast color. However, the use of too much water will retard drying time and warp the paper causing faulty registration. Accordingly, the water content of the pigment composition should be between about 5 percent to about 25 percent ofthe pigment composition. The particular pigments may be any of the well known dry pigments of the prior art,

such as rhodamine red, process red, process blue, process yellow, peacock blue, green, black, white and the like. In effect, any conventional pigment or mixture of pigments conventionally utilized in the coloring or printing trade can be utilized, the only requirement being that the pigment is not water soluble so that the same is not washed out in the washing step. Such pigmerit may be mixed with the alcohol-water solution in varying proportions depending upon the shade or intensity of the particular color desired. While the amount of pigment can vary considerably, it is preferred that the pigment or mixture of pigments be present in an amount of 1 percent by weight with the remainder of the pigment composition comprising the lower alkyl alcohol and minor amounts 'of other conventional adjuvants. One particularly effective pigment composition for use in this invention can be made as follows: One ounce of a 91 percent isopropyl alcohol, 9 percent water mixture is mixed with an effective amount of dry pigment and one-sixth of an ounce of calamine (zinc oxide-ferric oxide suspension). Such pigment composition possesses good stability and can thereby be easily matched to any printing ink color by well known tinting procedures or by pre-established color blending formulae.

While a wide choice of pigment blends and the great variety of paper substratesafford great versatility for the design artist, the remaining materials for the process of this invention may be easily adopted from existing relief image reproduction equipment. For example, the bichromate emulsion is a well known mixture of potassium bichromate (dichromate) crystals and gelatin. In accordance with a preferred embodiment of the present invention, the bichromate gelatin emulsion contains percent by weight gelatin, 0.5 l percent of the potassium bichromate crystals and the remainder, water. One suitable emulsion utilizes the following: About 1 ounce of gelatin is mixed in 4 ounces of tap water. The temperature of the water is not critical, but the hotter the water, the quicker the gelatin dissolves and mixes. One ounce potassium bichromate (dichromate) crystals is mixedinto 1 quart of cold tap water, the temperature again not being critical. One ounce of this potassium bichromate solution is then added to the gelatin mixture. This emulsion may then be used to coat the paper in the process hereinbefore set forth.

Since the bichromate emulsion is suitable for only a short period of time, it is preferable to make only enough emulsion for the work at hand. The sample emulsion mixture recited above, for example, makes approximately 5% ounces of emulsion which, in turn,

can be applied to approximately 1,870 square inches of paper.

The 1 ounce solution of potassium bichromate which has been mixed in l' quart of cold water can be stored in tinted glass and not lose its effectiveness for one month. The stability of this solution as well as the gelatin emulsion can be prolonged for a short period of time by storage in cold, dark areas.-

It is pointed out that where the amount of gelatin is less than about 15 percent of the bichromate gelatin emulsion, the color penetrates the gelatin and tints the surface of the paper, whereas more than about 25 percent gelatin causes the emulsion to thicken quickly and become unworkable. Also less than about 0.5 percent by weight of the potassium bichromate crystals has an adverse effecton the light sensitivity of the emulsion.

Other preparations, substitutes for gelatin, have been tested, such as gum arabic and albumin and have washed completely off the paper surface even though exposed to the same light.

In the event the emulsion has hardened, it can be returned to a liquid state by placing the hardened emulsion over a low flame or heat. The procedure of returning the hardened emulsion to a liquid state should not be done more than one time as the emulsion loses its sensitivity to light. In any event, emulsion mixed on one day should not be used the following day due to the loss of light sensitivity. If the emulsion is returned to a liquid state from a hardened state, it should only be done on the day that it was originally mixed.

Another important feature of this invention is the suitability of well known actinic light source as used in the printing art today.

Based on a 300 watt light bulb, the emulsion will not harden on the surface of the paper unless there is an elapsed time of 2 minutes or more. Once the separation negative is placed over the paper treated with the emulsion as mentioned before, 2 minutes are required for the emulsion to harden using a 300 watt bulb. Over exposure is not a critical factor for once the emulsion has hardened, it remains hardened. An arc lamp will reduce' the amount of light exposure time necessary to harden the emulsion, but the only critical factor is the actual hardening of the emulsion. The hardening of the emulsion is in direct proportion to the strength of the light. Distance of the light to the sheet of paper will also vary the hardening time of the emulsion, but this will also reflect in a proportionate basis as to the size of the paper and the size and strength of the light. The length of exposure is not critical as long as the emulsion hardens and the length of exposure can be shortened substantially upon an increase in the intensity of the light source.

Time is not a critical factor between the time the emulsion isaplied to the paper and then is exposed to as it dries, it becomes more sensitive to light. Drying time with a hot air blower will depend on the heat generated by the blower.

Once the emulsion is dry and is exposed through the separation negative to light, the next step is the application of the pigment. The wipe on or brush on of the pigment to the surface of the paper should also be done under subdued light. The term subdued light means ordinary roomlight. It does not require infrared or darkroom conditions. Normal printing shop lighting for normal working conditions will not affect the light sensitivity of the emulsion.

The pigment, due to the alcohol base, will dry at room temperature in approximately seconds due to natural evaporation. Application of the hot air blower to the pigment reduces the drying time proportionately to the heat generated by the hot air blower. The drying of the pigment again should be done under subdued light.

Once the pigment is dried on either or both sides of the paper it is then washed in water to wash off the unhardened emulsion and color. The temperature of the water is not critical but hot water gives the best results and the fastest washout. The length of time for the washout depends on the temperature of the water. The colder the water, the longer it takes to washout. For best results, the water should be at least 100F.

Following the washout, the paper is best dried by use of a hot air blower. It will dry naturally at room temperature, but a hot air blower reduces drying time to approximately 2 minutes depending on the heat generated by the blower. This is true whether or not both sides of the paper have been used.

After washing the paper, the same side as originally coated or both sides of the paper are coated with the bicromate gelatin emulsion a second time and this emulsion is thereafter dried as described above. The emulsion, when dried, is thereafter exposed through a second color separation negative to cause the gelatin to harden in the areas exposed by light and remain unhardened in the areas not so exposed. After exposing the emulsion through the second color separation negative, a second desired color, preferably in the form of a pigment composition comprising a volatile solvent, preferably a lower alkyl alcohol, water and pigment, is applied to the gelatin with subsequent drying as described earlier. After this application of the second desired color, the coated paper is again washed, preferably in hot water, to remove the unhardened gelatin with subsequent drying of the coated paper. The steps of coating the paper with the bichromate gelatin emulsion, exposing the emulsion through a color separation negative and applying the further desired color including the drying and washing steps can thereafter be repeated for each color desired. In this regard, the number of color which can be applied in the color proofing process of the present invention is virtually unlimited.

As described above, the color proofing process of the present invention is subject to certain variations, one of these, as mentioned earlier, is the coating of both sides of the paper with the bichromate gelatin emulsion and thereafter carryingout the foregoing processing steps with regard to each side of the paper simultaneously. This allows for the preparation of a suitable color proof on both sides of a paper in a manner not heretofore possible with conventional processes. Similarly, the

process of the present invention allows for overprinting in a single color application or in multiple applications by first applying a color to the exposed bichromate gelatin emulsion which can be overprinted and thereafter applying the color to effect the overprinting after coating the emulsion with a further bichromate gelatin emulsion and again exposing the emulsion through a color separation negative. In this embodiment of the present invention except for the overprinting of the color, the steps are essentially as described above.

Still further, it is pointed out that where black is being applied or where a black color is being produced through overprinting, overprinting can take place in a single color application in accordance with the process of the present invention. Still further, it should be recognized that where overprinting is not desired, more than one color can be applied through a single sequence of coating the paper with the bichromate gelatin emulsion, exposing the emulsion through a color separation negative and applying the desired color, the provision being that, in this instance, the multiple colors are applied to areas which do not touch.

Still further, it should be recognized that while the present invention has been described primarily with respect to applying multiple colors in a color proofing process, the steps described previously with respect to the application of a single color constitute a new and improved procedure for color proofing and such procedure is, of course, within the scope of the present invention.

The process of the present invention and the products produced thereby will be further seen by reference to the following examples, which examples are presented for purposes of illustration only and are in no way to be deemed as limiting the present invention.

EXAMPLE 1 A single color proof is produced by wiping an emulsion as prepared as follows onto an ordinary sheet of paper and allowing the emulsion to dry beneath a hot air blower.

The bichromate gelatin emulsion is prepared by adding approximately 1 ounce of gelatin (Knox unflavored gelatin) to about 4 ounces of tap water so as to dissolve the gelatin. One ounce of potassium bichromate crystals is mixed into a quart of tao water and 1 ounce of this potassium bichromate solution is added to the gelatin mixtureto form the final gelatin bichromate emulsion.

The coated paper is next exposed through a color separation negative to a light source for a period of 3 minutes. Next, a brown pigment composition prepared as follows is wiped on the dried emulsion and allowed to dry for 10 seconds.

The pigment composition is prepared by mixing 1 ounce of a 91 percent isopropyl alcohol 9 percent water mixture with an effective amount of dried pigment and one-sixth of an ounce of calamine (zinc oxideferric oxide suspension). in the case of this composition, a brown pigment is added with such brown pigment being replaced by other conventional pigments in the examples which follow.

Then, the coated paper is placed in a hot water bath and the unreacted gelatin emulsion is washed out. After the wash out, the paper is dried by fastening to a clean absorbent blotter and placed beneath a hot air blower until dry. The total process is complete in about 5 minutes and the proof is a clear, brown and white reproduction of the desired sample layout.

EXAMPLE 2 Two proofs are produced from the same treated paper using a different color for each proof and requiring only a single wash out of the coated emulsion. The first side of the paper is coated with emulsion, dried, exposed through the color separation negative and coated with pigment composition as in Example 1 and then turned over. The opposite side is then coated with an emulsion of the type set forth in Example 1 and allowed to dry. as previously described, exposed through a color separation negative, wiped with a blue pigment composition and dried for seconds, and then both sides of the paper are placed in hot water-for wash out of the unreacted gelatin emulsion. Drying takes place as in Example 1 and a two-sided proof with a different color on each side is produced in less than twice the time it takes to produce the single proof of Example 1.

EXAMPLE 3 paper in which the first color down is the same on both sides, but the second color down is different on the front and back of the paper.

a. An emulsion as prepared in'Example l is wiped on the front'surface of an 18 inch X 22 inch sheet of ordinary printing paper and fan dried;

b. The coated paper is exposed through a first color separation negative to a light source;

c. The first pigment composition, a blue color is wiped on the emulsion and allowed to dry.

d. The printing sheet is now turned over and coated on the back side with the emulsion as used in step (a) and allowed to dry as previously described;

e. Theemulsion is exposed as in step (b);

f. The sheet is coated with theblue pigment composition as instep (c) and allowed to dry;

g. The entire sheet issubjected to the wash out step by placing in hot water and rinsing out the unreacted gelatin emulsion and fan dried for a period of 2 minutes;

h. Steps (a), (b) and (c) are repeated utilizing a second color separation negative and a yellow pigment composition;

i. Steps (d), (e) and (f). are repeated utilizing a second color separationnegative and a red pigment composition; i

j. The entire sheet is washed in hot water as in step (g);

k. The sheet is finally fastened to an absorbent surface and allowed to dry completely.

The final result is a single sheet in which the blue and yellow frontside proof may be quickly compared to the blue and red back side proof. I

EXAMPLE 4 I The same procedures as in Example 3 are followed utilizing a colored sheet of craft paper as the emulsion substrate. This process adds a new dimension to the color proof by providing a pleasingly toned background to the color layout.

EXAMPLE 5 A four colored proof is produced by the following process:

a. Paper is fastened to a thin plastic sheet.

b. The emulsion prepared as in Example 1 is wiped on the paper and allowed to dry.

0. The coated paper is exposed to a light source through a black color separation negative.

d. A black pigment composition is wiped on the coated paper and allowed to dry.

e. The unreacted gelatin emulsion is washed outwith hot water and the paper is allowed to dry.

f. Steps (a) through (e) are repeated utilizing a yellow color separation negative and a yellow pigment composition.

g. Steps (a) through (e) are again repeated utilizing a magenta color separation negative and a magenta pigment composition.

h. Steps (a) through (e) are repeated'utilizing a cyan color separation negative and the corresponding cyan pigment composition. I

By carrying out the above procedure, a color proof is obtained with distinct areas of black, yellow, magenta and cyan.

EXAMPLE 6 The following procedure is followed to provide a two color proofing where black overprints the other color. In this process, two emulsions are usedwith a single wash out.

a. The emulsion prepared as in Example 1 is wiped on a single sheet of printing paper and allowed to dry.

b. The coated paper is exposed to a light source through a yellow separation negative.

0. The yellow pigment composition is wiped on and allowed to dry.

d. The color coated paper is rubbed down with a clean, lint-free material until a minimum of powder remains.

e. A second layer of emulsion is wiped on and allowed to dry. v

f. A negative for black is exposed to the light source.

EXAMPLE 7 Steps (a) through (g) of Example 6 are performed on one side of an ordinary sheet of printing paper. The paper is turned over and steps (a) through (g) of Example 6 are performed on the back side with a magenta color separation negative and magenta pigment composition being substituted for the yellow separation negative and pigment composition utilized on the front side. Then, the entire sheet is subjected to the wash out procedure of step (h) in Example 6 and dried to produce colorprints of two colors each with a single wash out step.

EXAMPLE 8 This example shows that proofing of two, three or more colors on one side or two sides of a sheet of paper with one emulsion and one wash out can be achieved if colors do not touch or overprint each other.

a. The printing paper is fastened to a plastic sheet.

b. The emulsion prepared as in Example 1 is wiped on the printing paper and allowed to dry.

c. All color separation negatives are exposed at one time to a light source.

d. A pigment composition corresponding to each colored area in the separation negatives is carefully painted in the appropriate area and allowed to dry.

e. The paper is removed from the plastic sheet, turned over and refastened to the plastic sheet.

f. Steps (b), (c) and (d) are repeated on the opposite side utilizing pigment compositions of different shades than those used on the front side.

g. The sheet is then removed from the plastic and all colors are washed out from both sides of the sheet at the same time in hot water.

h. Drying is accomplished by fastening the wet sheet to a clean blotter to absorb any excess moisture and then dried by a hot air blower.

EXAMPLE 9 Proofing three colors plus a fourth overprinting color is demonstrated by the following steps:

a. Steps (a) through (d) of Example 8 are performed utilizing yellow, magenta and cyan color separation negatives and corresponding color pigment compositrons.

b. The color coated paper is then rubbed with a clean, lint-free material until a minimum of powder remains.

c. A second layer of emulsion is wiped on and allowed to dry.

d. A negative for black is exposed to a light source.

e. A black pigment composition is wiped on and allowed to dry.

f. The sheet is subjected to a wash out procedure which removes the unreacted gelatin emulsion containing the overprinted colors and the black color.

This process may also be performed on both sides of a single sheet of paper utilizing a single wash out for the entire four-color process.

EXAMPLE 10 Printing plates for the full color comprehensives of Example 5 are made up and final prints are produced to compare with the color proofs of Example 5. On comparison, the proof can not be identified by an untrained person when placed at random in a group of the final prints. As a follow-up comparison, the proofs and final prints are inspected after 6 months storage to determine any change in color of the proofs. As in the original comparison, no discernible variations in color are detected. Therefore, the surprising stability of the color proofs of the present invention demonstrate a further advantage to this process.

EXAMPLE 1 1 An experiment is performed to determine the reproduceability of the color proofs after a period of time and with newly made pigment compositions. In

this experiment, the process as set forth in Example 5 is carefully performed using entirely different batches of pigment compositions than are used in Example 5. The new batches of pigment compositions are made according to the formulae used for the first pigment batches with no tinting or adjustment being performed. Proofs are made from the second batch of pigment compositions and when compared to the proofs from the first pigment composition batches show a surprising degree of color matching. This ability to reproduce the nearly identical colors from different batches of pigment compositions is believed to be due to the simplicity of the process of this invention, the availability of the materials used in the process and the stability of the pigment compositions themselves.

It can be seen from the foregoing examples that the process of the present invention provides a novel means for color proofing, the proofs obtained being virtually indistinguished from the final prints, the process of the present invention being simple and inexpensive for carrying out the objects and advantages noted previously. In this regard, the present invention produces a distinct advance in the environment of color proofmg.

While the present invention has been described primarily with regard to the foregoing exemplification, it is to be understood that the present invention is in no way to be deemed-as limited thereto but rather must be construed as broadly as all or any equivalents thereof.

What is claimed is: I l. A process for color proofing comprising:

2. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same;

b. exposingsaid emulsion to light through a first color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

c. apply a first desired color on the hardened and unhardened gelatin and drying the coated paper;

d. washing the coated paper to remove the unhardened gelatin and drying the coated paper;

e. coating the same side of said paper as in step (a) with a bichromate gelatin emulsion a second time and driving the same;

f. exposing the emulsion of step (e) through a second color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

g. apply a second desired color to the hardened and unhardened gelatin and drying the coated paper; and

- h. washing the coated paper to remove the unhardened gelatin and drying the coated paper.

2. The process of claim 1 wherein the color is applied to the coated paper in the fon'n of a pigment composition comprises a lower alkyl alcohol, water and pigment.

3. The process of claim 2 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.

4. The process as in claim 1 wherein the emulsion coating step (a), exposing step (b), color application step (c) and washing step (d) are repeated for each additional color desired.

5. The process as in claim 1 wherein the coating step (a), exposing step (b) and color application step (c) are performed on both sides of said paper before washing the coated paper to remove the unhardened gelatin from both sides.

6. A process for color proofing comprising:

a. coating a paper on at least one side with a bichromate gelatin emulsion and drying the same;

b. exposing the emulsion through a first color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

c. applying a color which'can be overprinted and drying the coated paper;

d. coating the same side of said paper as in step (a) with a bichromate gelatin emulsion a second time and drying the same;

.e. exposing the emulsion through a color separation negative for an overprinting color to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

f. applying said overprinting color and drying the coated paper; and I g. washing the coated paper to remove the unhardened gelatin and drying the coated paper.

7. The process of claim 6 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.

8. The process of claim 6 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.

9. The process as in claim 6 wherein steps (a) through (f) are performed on both sides of the paper prior to the washing step (h).

10. A process for color proofing comprising:

a. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same;

b. simultaneous exposing'the emulsion through two or more color separation negatives to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

c. applying a color to the desired areas of the emulsion and drying the coated paper; and

d. washing the. coated paper to remove the unhardened gelatin and drying the coated paper.

11. The process of claim 10 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.

12. The process of claim 10 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition;

13. The process of claim 10 wherein steps (a), (b) and (c) are performed onboth sides of the paper before performing the washing out step (d).

14. A process for color proofing comprising:

a. coating at least one side of a paper with bichromate gelatin emulsion and drying the same;

b. exposing the emulsion through two or more color separation negatives which may be overprinted to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

c. applying the colors which may be overprinted to the desired areas of the emulsion and drying the coated paper;

(1. coating the same side of said paper with a bichromate gelatin emulsion a second time and drying the same;

e. exposing the emulsion through the overprinting color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

f. applying the overprinting color and drying the coated paper; and

g. washing out the coated paper to remove the unhardened gelatin and drying the coated paper.

15. The process of claim 14 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol,,water and pigment.

16. The process of claim 15 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition. v

17. The process as in claim 14 wherein steps (a) through (f) are performed on both sides of the paper before performing the washing out step (g).

18. A process for color proofing comprising:

a. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same;

b. exposing the emulsion through a color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed;

c. applying a pigment composition comprising a lower alkyl alcohol, water and pigment and drying the coated paper; and

d. washing out the coated paper in hot water to remove the unhardened gelatin and drying the coated paper.

19. The process of claim 18 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pig ment.

20. The process of claim 19 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.-

21. The process of claim 18 wherein the steps (a), (b) and (c) are performed on both sides of the paper before the washing out step (d). 

2. The process of claim 1 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.
 2. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same; b. exposing said emulsion to light through a first color separation negative to cause the gElatin to harden in areas exposed to light and remain unhardened in areas not exposed; c. apply a first desired color on the hardened and unhardened gelatin and drying the coated paper; d. washing the coated paper to remove the unhardened gelatin and drying the coated paper; e. coating the same side of said paper as in step (a) with a bichromate gelatin emulsion a second time and driving the same; f. exposing the emulsion of step (e) through a second color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; g. apply a second desired color to the hardened and unhardened gelatin and drying the coated paper; and h. washing the coated paper to remove the unhardened gelatin and drying the coated paper.
 3. The process of claim 2 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.
 4. The process as in claim 1 wherein the emulsion coating step (a), exposing step (b), color application step (c) and washing step (d) are repeated for each additional color desired.
 5. The process as in claim 1 wherein the coating step (a), exposing step (b) and color application step (c) are performed on both sides of said paper before washing the coated paper to remove the unhardened gelatin from both sides.
 6. A process for color proofing comprising: a. coating a paper on at least one side with a bichromate gelatin emulsion and drying the same; b. exposing the emulsion through a first color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; c. applying a color which can be overprinted and drying the coated paper; d. coating the same side of said paper as in step (a) with a bichromate gelatin emulsion a second time and drying the same; e. exposing the emulsion through a color separation negative for an overprinting color to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; f. applying said overprinting color and drying the coated paper; and g. washing the coated paper to remove the unhardened gelatin and drying the coated paper.
 7. The process of claim 6 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.
 8. The process of claim 6 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.
 9. The process as in claim 6 wherein steps (a) through (f) are performed on both sides of the paper prior to the washing step (h).
 10. A process for color proofing comprising: a. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same; b. simultaneous exposing the emulsion through two or more color separation negatives to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; c. applying a color to the desired areas of the emulsion and drying the coated paper; and d. washing the coated paper to remove the unhardened gelatin and drying the coated paper.
 11. The process of claim 10 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.
 12. The process of claim 10 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.
 13. The process of claim 10 wherein steps (a), (b) and (c) are performed on both sides of the paper before performing the washing out step (d).
 14. A process for color proofing comprising: a. coating at least one side of a paper with bichromate gelatin emulsion and drying the same; b. exposing the emulsion through two or more color separation negatives which may be overprinted to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; c. applying the colors which may be overprinted to the desired areas of the emulsion and drying the coated paper; d. coating the same side of said paper with a bichromate gelatin emulsion a second time and drying the same; e. exposing the emulsion through the overprinting color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; f. applying the overprinting color and drying the coated paper; and g. washing out the coated paper to remove the unhardened gelatin and drying the coated paper.
 15. The process of claim 14 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.
 16. The process of claim 15 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.
 17. The process as in claim 14 wherein steps (a) through (f) are performed on both sides of the paper before performing the washing out step (g).
 18. A process for color proofing comprising: a. coating at least one side of a paper with a bichromate gelatin emulsion and drying the same; b. exposing the emulsion through a color separation negative to cause the gelatin to harden in areas exposed to light and remain unhardened in areas not exposed; c. applying a pigment composition comprising a lower alkyl alcohol, water and pigment and drying the coated paper; and d. washing out the coated paper in hot water to remove the unhardened gelatin and drying the coated paper.
 19. The process of claim 18 wherein the color is applied to the coated paper in the form of a pigment composition comprises a lower alkyl alcohol, water and pigment.
 20. The process of claim 19 wherein the water content of said pigment composition is from about 5 percent to about 25 percent by weight, based on the weight of the entire pigment composition.
 21. The process of claim 18 wherein the steps (a), (b) and (c) are performed on both sides of the paper before the washing out step (d). 